Electric lamp



Oct. 31, 1939. E. FRIEDERICH ELECTRIC LAMP Filed Aug. 10, 1957 INVENTQR 552;: Frlederyh Patented Oct. 31, 1939 UNITED STATES PATENT OFFICE 2,111,105 nmc'rmc LAMP Application August 10, 1937, Serial No. 158,425

In Germany August 11, 1936 4 Claims.

The present invention relates to electric lamps and more particularly the invention relates to such lamps of the type which produce light by electronic bombardment of suitable substances.

5 Electric lamps of this type comprise a source of electrons mounted in a sealed, vitreous envelope and a material in said envelope capable of emitting light when bombarded by the electrons from said source. The light emitting material is aplo plied to the inner wall of the envelope or to special anodes in the envelope. A large number of well known chemical compounds, particularly those which are capable of light emission under excitation by ultra violet light, are useful as light emitting materials in lamps of this type. Such materials are poor electrical conductors and additional means must be employed to carry oi! the electrical energy of the electrons to prevent the formation of an electron sheath about the light emitting material. Such a sheath would prevent the electron bombardment of the material thus diminishing or preventing the emission of light by such material; This electrical characteristic of such materials has been recognized in the past and the addition of powdered conducting substances, such as metals or electrically conducting sulphides, has been proposed. These admixed powders, however, are darkly colored and almost completely absorb the light. For this reason the so conducting powder has to be limited in quantity,

in order to get any light at all; but then, on the other hand, the purpose of the admixture of the powder, that is, a sufficiently active conduction for the current, is not obtained. A fine network of metallic conductors (wire mesh), also proposed heretofore, does not suiiice for the purpose, since the mesh opening necessarily cannot be too small.

The object of the present invention is to avoid the above disadvantages in lamps of the above type. Still further objects and advantages attaching to the device and to its use and operation will be apparent to those skilled in the art from the following particular description.

Theinvention attains its object by using a layer of electrically conducting, translucent material as the current abductor for the electrons. Zinc oxide is anexcellent material for this purpose. The

use of the zinc oxide as special abducting layer for this purpose was not known hitherto. The

zinc oxide is applied on the inner wall of the bulb or on a special surface inside of the glass bulb,

and on the zinc oxide layer, the layer which becomes luminous under the electron bombardment, is then produced. In this case the lightradiation can pierce the white zinc oxide and reach the outside without further ado. Such a lamp gives the impression of a matte-glass lamp, and therefore has the advantage of a uniform distribution of the radiation. With the arrangement according to the invention it is desirable I that every smallest particle of the layer of the luminous substance lies directly on a bright, transmissive or also reflecting layer of a conductor for the electric current, so that both lightradiation and current abduction can proceed un- 10 disturbed.

In the drawing accompanying and forming part of this specification an embodiment of the invention is shown in a front elevational, sectional view. 1

Referring to the drawing the lamp device comprises an evacuated, sealed, vitreous envelope I having a thermionic, activated electrode mounted therein. The thermionic electrode is of the Hull type and consists of a metal shell I! having a heating filament 9 therein and a coating of electron emitting material, such as barium oxide on the outer surface of said shell It. One end of said filament 8 is connected to the current lead 8 and the opposite end thereof is connected to the 25 metal shell Ill. Said shell II is connected to and supported bya current lead I. Said leads I and 8 are fused into the press of the stem I fused to said envelope I. Said electrode 9, l0 emits electrons when heated by the passage of current 30 therethrough.

A layer 2 of zinc oxide is applied to the inner surface of the envelope l as by dusting. When desired, the zinc oxide coating is produced by vaporizing zinc onto the envelope wall and then 88 oxidizing the zinc. The resistance of the zinc oxide coating is reduced by heating in the vacuum. A resistance in the order of about 1 to 10 ohms per cm. is preferable. When desired, the electrical conductivity of the zinc oxide, which is 40 due to a small, hardly detectable lack of oxygen, can be produced or improved by using chemical reducing agents, such as traces of organic binding agents, for the zinc oxide powder or by the use of gaseous reducing agents such as hydrogen. 45 Other bright colored oxides or compounds also fulfill the purpose of the-present invention, such as niobpentoxide.

The coating 3 of material capable of emitting light under electron bombardment is applied to 50 the zinc oxide coating 2. Said coating 3 consists of any of the well known materials used heretofore, such as calcium tungstate. The zinc oxide coating 2 is connected to a current lead I fused in said stem 4 by applying a metal powder to the in- I ner surface 01' the envelope l which powder is burned into the surface of the glass and connected to the lead I and the coating 2. When desired the current lead 1 is soldered to the metal powder.

The lamp described above is an eflicient light source. I'he zinc oxide coating 2 is transparent to the light rays emitted by the material of coating 3 which emits light under bombardment by the electrons emitted by the thermionic electrode Hi.

When desired the zinc oxide coating, which is white in appearance, is used as on a reflecting element in the container. In this embodiment of the invention a metallic base is mounted inside of the envelope I in a position such that the light emitted by the light emitting material is sent out in a desired direction. Preferably the base is a bright one and is connected as the anode. The zinc oxide layer is applied to said base and the layer of light emitting material is applied to said layer of zinc oxide.

While I have shown and described and have pointed out in the annexed claims certain novel features of the invention, it will be understood that various omissions, substitutions and changes in the forms and details of the device illustrated and in its use and operation may be made by those skilled in the art without departure from the broad spirit and scope of the invention, for example, a'cataphoretic process is used for applying the zinc oxide coating, when desired, the zinc oxide coating is applied directly onto a layer of zinc, when desired and a slight amount of gas,

such as argon, is introduced into the envelope l to reduce the space charge, when desired.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric discharge device comprising a sealed vitreous envelope, an anode, a source of electrons and a material which emits light under bombardment by the electrons from said source in said envelope, one surface of said anode consisting of an electrically conducting oxide and supporting said light emitting material, said oxide layer consisting of material from the group consisting of zinc oxide and niobpentoxide, said light emitting material being interposed between said electron source and said oxide.

2. An electric lamp comprising a sealed vitreous envelope, an anode, a source of electrons and a material which emits light under bombardment by the electrons from said source in said envelope, one surface of said anode consisting of zinc oxide and supporting said light emitting material, said light emitting material being interposed between said electronsource and said oxide.

3. An electric lamp comprising a sealed vitreous envelope containing a source of electrons, a material which emits light under bombardment by the electrons from said source and a niobpentoxide layer supporting said light emitting material.

4. An electric lamp comprising a sealed vitreous envelope, an anode, a source of electrons and a material which emits light under bombardment by the electrons from said source in said envelope, said anode consisting of an electrically conducting oxide layer supporting said light emitting material and a metal body having a bright reflecting surface to which said oxide layer is applied, said oxide layer consisting of material from the group consisting of zinc oxide and niobpentoxide, said light emitting material being interposed between said electron source and said metal body.

ERNST FRIEDERICH. 

